High-Sensitivity Strain Sensing Using a Flexible Microstrip Antenna With Metamaterial Resonator

This article presents a flexible strain sensor based on a coplanar microstrip antenna designed to detect strain by measuring changes in resonant frequency within the industrial, scientific, and medical (ISM) band. The design integrates a Y-shaped monopole antenna with an open-ring resonator, which enhances sensitivity. The design process utilized a computational methodology grounded in a multiphysics approach, which effectively coupled mechanical and electromagnetic phenomena. Additionally, the sensor was manufactured using the screen-printing technique and subsequently validated through experimental testing. The results indicate that the proposed sensor achieves sensitivities of 20.788 and 17.42 kHz/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula> for convex and concave deformations, respectively. The computational simulations closely matched the experimental outcomes, further verifying the efficiency of the proposed design and the robustness of the computational model. The study also explored the impact of the polylactic acid (PLA) support’s thickness on sensor performance, demonstrating that maximum sensitivity (106 kHz/<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \varepsilon $ </tex-math></inline-formula>) is achieved in the absence of the PLA support. This indicates that the support material significantly limits sensor mobility, thereby reducing sensitivity. The proposed antenna sensor is cost-effective and exhibits high strain-detection capabilities, presenting promising applications for structural health monitoring (SHM) systems.